Vascular access includes any procedure wherein a needle is used to puncture a vein or artery. The most common forms of vascular access are intravenous (IV) catheter insertion for the delivery of fluids, phlebotomy sticks for extracting venous blood samples, and arterial sticks for extracting arterial blood samples. There are two main difficulties in vascular access: locating the vein or artery and precisely aiming and moving the needle into the vessel.
Locating veins and arteries is often difficult because they sit beneath layers of skin and fat. In healthy men and many elderly patients, veins can be seen and felt readily at common insertion locations such as the hands and arms. However, many women and children do not have easily-locatable veins. Arteries are located deeper than veins and cannot be seen with the naked eye. However, some arteries can be located very roughly through palpating for the patient's pulse. Infrared (IR) light can be used to see veins and arteries because blood absorbs IR light much more readily than do the tissues that surround the vessels targeted for vascular access. Accordingly, an infrared picture of a vein or artery shows the vessel as dark on a light background.
Precisely aiming and moving a small needle into a vein or artery that is not much bigger than the needle can be challenging, particularly in smaller patients such as infants and children. Aligning the needle at the desired initial angles and insertion point can typically be half of the problem. To obtain an accurate estimate of the insertion point, the needle tip must be kept close to the surface of the skin. However, a small, aberrant motion could nick the skin and injure the patient. Even a small nick could produce enough blood to obscure the insertion point for a considerable time while the nick clots, or can cause local vasoconstriction (shrinking) of the surrounding vessels, making insertion much more difficult. However, keeping the needle tip at a larger, safer distance from the skin while aligning the needle provides a less accurate visual estimate of the insertion point, increasing the chances of missing the targeted vessel.
What is needed and is not provided by the prior art are methods and devices for assisting medical practitioners with locating access points in veins and arteries, and for assisting practitioners with safely and precisely aiming an access needle at the insertion point with a desired needle trajectory during vascular access.